Whether or not you bought into all the hoopla, one thing’s for sure: the island to which ABC's series Lost transported us for six years was one strange place. A good chunk of its mystique, however, could be explained by a powerful electromagnetic force field that acted as its invisibility cloak and sent the island’s residents hurtling through time, all the while stopping people from coming and going as they pleased.

But what if Lost's barrier to the outside world wasn’t just a phantom force that crashed planes—what if, instead, it was a real, tangible roadblock? Here, we take a look at some architectural barriers from mythology and pop culture that take on a distinctly spatial form.

Alexander’s Gates

Alexander the Great supposedly built a mythic wall during the fourth century B.C. to keep barbarians locked out of the Caucasus, a region on the border of Europe and Asia. It’s said that he chased his enemies through a mountain pass and then trapped them there behind huge locked gates, forming what author Stephen Asma has called a "monster zone" where the enemies of Europe could be kept at bay. Oddly enough, Alexander's Gates were depicted in most maps dating back to those years. Over time, however, the legend of the Gates has become associated with the remains of the Caspian Gates in the Russian city of Derbent, although the credit is a tad misplaced: those walls were most likely built by a Persian king who ruled more than 800 years after Alexander's time.

U.S.-Mexico Border, Monsters (2010)

In the British sci-fi film Monsters, a deep space probe crash-lands in Northern Mexico, bringing with it a host of extraterrestrial beings native to Jupiter's moon Europa. To combat the spread of these creatures past their Mexican turf, known as the "Infected Zone," Mexico and the United States collaborate to build a huge wall along their mutual border. Six years after the probe careened into Earth's atmosphere, it's clear that keeping these monsters under control is no easy feat: they've colonized the entire width of the country, from the Pacific Ocean to the Gulf of Mexico, even with the wall in place. (An obvious parallel can be drawn here to the very real issue of border control and undocumented "aliens.")

The Labyrinth at Crete

The original labyrinth was famously ordered by King Minos of Crete and designed by the artisan Daedalus. Its purpose was to lock up the half-man, half-bull Minotaur, a monstrous product of (what else?) ancient bestiality. The maze was so elaborate, in fact, that Daedalus himself nearly got lost in it. When Theseus later ventured into the darkness to take on the Minotaur in battle, he had to unravel a ball of string as he proceeded along its halls so that he'd be able to find his way out after slaying the monster. We still don't have proof that this labyrinth actually existed—but some people argue that the complex floor plan of Minos's palace at Knossos could have inspired the original myth.

Skull Island Wall, King Kong

When King Kong first stomped onto movie screens in 1933, the prehistoric ape's mythic backstory placed his origins on the remote Skull Island, off the coast of Indonesia. It's littered with prehistoric creatures—dinosaurs, birds of prey, overgrown spiders, and of course, Kong, ape lord of the rain forest. The creatures have managed to coexist in at least some fashion with the island's native inhabitants, a relationship eased by the occasional human sacrifice. A steep wall, however, with a locked gate encircles the jungle encampment and puts some distance between the animals and the overgrown animals for years—although, in the end, it's no match for Kong. He eventually forces his way to the sacrificial altar and runs into the night with Ann Darrow.

Pluto's Gate

This shrine to Greco-Roman god Pluto was touted as the "portal to the underworld" in ancient times. The temple was built over a cave that had toxic gas flowing through it, gas that was thought to be sent by Pluto himself. Setting foot down the staircase and into the cave granted a death wish, unless you were particularly skilled at holding your breath and finding pockets of oxygen; otherwise, you'd stumble headlong into carbon dioxide fumes, a result of activity beneath the Earth's crust. Earlier this year, archaeologists dug up what they believe to be the site of Pluto's Gate in southwest Turkey—though that theory might be a tad difficult to test.

Kaiju Wall, Pacific Rim (2013)

This summer saw the release of Pacific Rim, which brought us more monsters-on-Earth angst. When dragon-like creatures known Kaijus break through from another dimension using a mysterious portal in the Pacific seabed, the natural response of the Pacific Rim countries is to build lots and lots of robots to take on the towering beasts. In 2025, after 12 years of fighting off the Kaijus and pouring resources into their Jaeger robot program, they are forced to resort to an old trick, constructing protective walls along the entire Pacific coast. As it turns out, man-made walls don't exactly wield the same power in the near dystopian future.